-
Approved Continuing Education for Licensed Professional
Engineers
Fundamentals of Biodiesel
Four (4) Continuing Education Hours Course #ME1275
EZ-pdh.com Ezekiel Enterprises, LLC
301 Mission Dr. Unit 571 New Smyrna Beach, FL 32170
[email protected]
https://ez-pdh.com/
-
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
ii
Course Description: The Fundamentals of Biodiesel course
satisfies four (4) hours of professional development. The course is
designed as a distance learning course that overviews biodiesel and
biodiesel blends and practical guidelines for using in place of
standard diesel.
Objectives: The primary objective of this course is to enable
the student to understand biodiesel and biodiesel blends, its
characteristics, storage and safety issues, and procedures for
using in compression-ignition engines and boilers.
Grading:
Students must achieve a minimum score of 70% on the online quiz
to pass this course. The quiz may be taken as many times as
necessary to successful pass and complete the course. A copy of the
quiz questions are attached to last pages of this document.
-
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
iii
Table of Contents Fundamentals of Biodiesel
Introduction
...........................................................................
1
Biodiesel Basics
......................................................................
3
Biodiesel (B100)
.....................................................................
8
Biodiesel Blends
...................................................................
20
Safety, Health, and Environmental Issues
.............................. 32
Glossary
...............................................................................
33
Appendix A: Sample Biodiesel Safety Data Sheet
........................ 35
Appendix B: Biodiesel Materials Compatibility Summary Tables .
43
Quiz Questions
.....................................................................
52
-
This course is a guide for those who blend, distribute, and use
biodiesel and biodiesel blends. It provides basic information on
the proper and safe use of bio-diesel and biodiesel blends in
engines and boilers, and is intended to help fleets, individual
users, blenders, distributors, and those involved in related
activities understand procedures for handling and using biodiesel
fuels.
Biodiesel is manufactured from plant oils, animal fats, and
recycled cooking oils and has several advantages. Biodiesel:
• Is renewable
• Displaces petroleum-derived diesel fuel
• Can be used in most diesel equipment withno or only minor
modifications
• Can reduce global warming greenhouse gasemissions
• Is compatible with new technology diesel engines(NTDE) and
emissions control devices
• Can reduce tailpipe emissions from oldervehicles, including
air toxics
• Is nontoxic, biodegradable, and suitable forsensitive
environments
• Is produced domestically from agricultural orrecycled
resources.
In this course, biodiesel refers to the fuel produced from
renewable sources that meets ASTM International (ASTM) Standard
D6751-15cε1 (the latest standard for biodiesel used as a
blendstock). A number following the letter “B” indicates the
percent by volume (vol%) of bio-diesel in a gallon of fuel; the
remainder of the gallon can be No. 1 or No. 2 diesel, kerosene, Jet
A, JP8, heating oil, or any other distillate fuel. Pure (or neat)
biodiesel is also known as B100.
Biodiesel is most commonly used as a blend with petro-leum
diesel. At concentrations of up to 5 vol% (B5) in conventional
diesel fuel, the mixture will meet ASTM D975 diesel fuel
specification and can be used in any application as if it were neat
petroleum diesel; for home
Introduction
heating oil, B5 will meet the ASTM D396 home heating oil
specification.1 At concentrations of 6% to 20% (B6 to B20),
biodiesel blends can be used in many applications that use diesel
fuel with minor or no modifications to the equipment, although not
all engine manufacturers have approved these blends for use in
their equipment. B6 to B20 blends are covered by ASTM Specification
D7467-15cε1. Biodiesel can even be used as a fuel in its neat form
(B100) if proper precautions are taken. Appendix A shows a sample
Safety Data Sheet for biodiesel.
Commonly used blends are limited to B20 in the United States
because this level provides a good balance between material
compatibility, cold weather oper-ability, performance, and emission
benefits, as studied. B20 is also the minimum blend level allowed
for compli-ance with the Energy Policy Act of 1992 (EPAct), which
requires the use of renewable fuels and/or alternative fuel
vehicles (AFVs) by certain covered fleets. Equip-
ASTM International (astm.org) is a consensus-based volunteer
standards group that comprises experts across numerous industries.
Commit-tee D02, Petroleum Products, Liquid Fuels, and Lubricants,
covers biodiesel, diesel, and heating oil specifications (in
addition to many other prod-ucts). Membership in D02 includes
engine and fuel injection equipment companies, fuel produc-ers, and
fuel users. ASTM standards are recog-nized in the United States by
most government entities. Specifications are living documents and
may be updated frequently to reflect the most current needs of the
industry. Any ASTM method or specification will include a number
and a year, such as D6751-15cε1. This means the most current
version of the method was published in 2015; a letter after the
year indicates that more than one modification has been published
in a given year. It is up to users to ensure they are using the
most up-to-date version of a test method or specification.
1. The ASTM standard for B100 to be used as a blend stock is
D6751. Diesel fuel is defined in ASTM D975. ASTM D396 defines
heating oils. A-A-59693A defines B20 for military use.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
1
http://astm.org
-
ment that can use B20 includes diesel engines, fuel oil and
heating oil boilers, and turbines.
Higher blend levels such as B50, and B100 require special
handling and may require equipment modifica-tions. These issues can
potentially be managed with heaters and/or changing engine seal and
gasket mate-rials. Consult your engine or combustion equipment
manufacturer for further information about procedures before using
biodiesel blends higher than B20.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
2
-
This section provides a basic overview of biodiesel. You can
also refer to Section 9 (Frequently Asked Questions) for answers to
general questions from your management, customers, or reporters.
Technical details about many aspects of biodiesel are provided in
Sections 3 to 8.
What is Biodiesel?
Biodiesel is a diesel replacement fuel for use in diesel
engines. It is manufactured from plant oils (e.g., soybean oil,
cottonseed oil, canola oil, corn oil); recycled cooking greases or
oils (e.g., yellow grease); or animal fats (beef tallow, pork
lard); and various com-binations of these feedstocks. Used cooking
oils are mostly plant based, but may also contain animal fats. Used
cooking oils are both recycled and renewable.
As biodiesel production and use increase, new feed-stocks are
being developed and may soon be introduced into the market. Some
examples include pennycress, camelina, cuphea, brown grease, and
various strains of algae. Although there is little biodiesel from
these feedstocks currently available, there is great potential for
these feedstocks to supplement the current feedstock supply.
The biodiesel manufacturing process converts oils and fats into
chemicals called long-chain mono alkyl esters, or biodiesel. These
chemicals are also referred to as fatty acid methyl esters (FAME),
and the process is referred to as esterification. Figure 1 provides
a sim-plified diagram of the esterification process. Roughly
speaking, 100 pounds of oil or fat are reacted with 10 pounds of a
short-chain alcohol (usually methanol) in
the presence of a catalyst (usually sodium hydroxide or
potassium hydroxide) to form 100 pounds of biodiesel and 10 pounds
of glycerin (or glycerol). Glycerin is a sugar and is a co-product
of the biodiesel process.
Biodiesel is a legally registered fuel and fuel additive with
the U.S. Environmental Protection Agency (EPA). The EPA
registration is feedstock and process agnostic and includes all
biodiesel that meets the ASTM bio-diesel specification, ASTM
D6751.2
Straight Vegetable Oil and Other Products
Raw or refined plant oils, fats, or recycled greases that have
not been processed into biodiesel, such as straight vegetable oil
(SVO), are not biodiesel and should be avoided. Research shows that
plant oils, animal fats, and/or greases used in diesel engines,
even at concentra-tions as low as 1%, can cause long-term engine
deposits, ring sticking, lube oil gelling and other maintenance
problems, and can reduce engine life. These problems are caused
mostly by the much higher viscosity, or thickness, of the raw fats
and/or oils (around 40 square millimeters per second [mm2/s])
compared to that of diesel fuel, for which the engines and
injectors were designed (1.3 to 4.1 mm2/s). The significantly
higher boiling point of raw fats and oils may also lead to failure
of the fuel to fully evaporate, especially during cold start,
leading to harmful engine deposits and engine oil sludging. Through
the process of converting plant oils or greases to biodiesel by
esterification, the viscosity and boiling point of the fuel are
reduced to values more similar to conventional diesel fuel
(biodiesel viscosity values are typically 4 to 5 mm2/s).
Biodiesel Basics
Vegetable Oil/Animal Fat/Waste
CrudeBiodiesel
Crude Glycerin
Biodiesel
Glycerin
Methanolplus Catalyst Esterification
GlycerineRefining
MethanolRecovery
Refining
Figure 1. Basic Esterification Process
2. astm.org.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
3
http://www.astm.org
-
Other products, many of which are offered to consum-ers without
the benefit of EPA registration, ASTM spec-ifications, or extensive
testing and demonstrations, may be mislabeled as “biofuels,”
“renewable diesel,” or even as “biodiesel.” It is up to the
consumer to be aware of what they are purchasing. If you purchase
methyl esters that do not meet ASTM biodiesel standards, it is not
legal biodiesel and should not be used in diesel engines or other
equipment designed to operate on diesel fuel. Methyl esters are
used as an industrial lubricant and solvent in some applications,
so be sure to purchase only ASTM D6751-grade methyl esters
(biodiesel) for use in diesel engines.
Specifications and Regulations
Specification D6751 is based on a compilation of efforts from
researchers, engine manufacturers, petroleum companies and
distributors, and many other fuel-related entities and is intended
to ensure the quality of biodiesel used as a blendstock at 20%
(B20) and lower blend levels. Any biodiesel used in the United
States for blending should meet ASTM D6751 standards. The ASTM
standards provide a minimum level of quality for biodiesel
regardless of the source of the fuel. Purchasers and sellers can
require that biodiesel meet more strin-gent requirements in
purchasing specifications. Both parties must agree to these more
stringent requirements, and this is becoming an increasingly common
practice.
The ASTM D6751 definition of biodiesel states that bio-diesel is
composed of “mono-alkyl esters of long-chain fatty acids derived
from plant oils or animal fats.” The term mono-alkyl esters
indicates that biodiesel contains only one ester linkage in each
molecule. Raw or refined plant oils, animal fats, and greases
contain three ester linkages and are therefore not legally
biodiesel. Bio-diesel can be made from methyl, ethyl, isopropyl,
and other alcohols. Virtually all commercial biodiesel pro-duction
in the United States today is based on methyl esters. Some research
has been conducted on ethyl esters (biodiesel produced with ethanol
as the alcohol rather than methanol); however, higher ethanol
prices relative to methanol, lower ethyl ester conversions, and the
difficulty of recycling excess ethanol from the finished biodiesel
have hampered ethyl ester production in the marketplace. Therefore,
in this course we will consider only methyl esters.
The definition of biodiesel recognized by both the EPA for fuel
registration purposes and the Internal Revenue Service for the
blender’s tax credit is essentially the same as the definition in
ASTM D6751:
“A fuel comprised of mono-alkyl esters of long-chain fatty acids
derived from vegetable oils or animal fats, designated B100, and
meeting the requirements of ASTM D6751.”
EPAct requires that certain federal, state, and alterna-tive
fuel provider fleets acquire a fixed percentage (75% or 90%) of
AFVs each year based on the total number of light-duty vehicles
they acquire. A light-duty vehicle that is approved by the original
equipment manufac-turer (OEM) to operate on B100 or a biodiesel
blend of B20 or higher qualifies as an AFV under EPAct. As of 2015,
there are no light-duty vehicles on the market approved to operate
on B100, but there are many that are approved to operate on B20.
Neat biodiesel may be more expensive than other alternative fuel
options, and OEMs have shown little interest in obtaining approval
for on-road vehicles to operate on B100.
Congress amended EPAct through the Energy Con-servation
Reauthorization Act of 1998. Among other things, the Energy
Conservation Reauthorization Act added Section 312 to EPAct,
thereby enabling covered federal, state, and alternative fuel
provider fleets to earn AFV credits for their use of B20 or higher
blends in medium- or heavy-duty vehicles (those vehicles with a
gross vehicle weight rating of more than 8,500 pounds), with some
limitations. This provision has created significant demand for B20
among government and alternative fuel provider fleets (Appendix
B).
How is Biodiesel Different than Renewable Diesel?
Renewable diesel is a hydrocarbon diesel fuel produced from
renewable feedstocks. Today, all renewable diesel on the market is,
like biodiesel, pro-duced from fats and oils. The way these fats
and oils are reacted into fuels is the defining difference between
biodiesel and renewable diesel. As discussed above, biodiesel is
primarily made through esterification. Renewable diesel is produced
by hydroprocessing of fats and oils. Hydroprocessing produces
alkanes, which are chemically identical to some of the compounds
found in conventional diesel fuel. The properties of renewable
diesel are also different from biodiesel. Like biodiesel, renewable
diesel has near-zero aromatic content and very low sulfur content.
It typically has a very high cetane number and a cloud point more
like conventional diesel fuels. When used as a neat fuel (RD100),
RD100 qualifies as an EPAct alternative fuel, while lower blends,
such as RD20, do not.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
4
-
The only way to determine if diesel fuel has been blended with
renewable diesel fuel is through carbon dating using ASTM D6866. In
this method, the iso-topic ratio of fossil to biological carbon is
quantified. Petroleum diesel will be wholly fossil carbon, while
the renewable diesel (or biodiesel) content will be identified as
biogenic carbon.
Benefits of Biodiesel Use
Biodiesel Reduces Greenhouse Gas Emissions
When biodiesel displaces petroleum, it significantly reduces
life-cycle greenhouse gas emissions. Life cycle analysis completed
by Argonne National Laboratory found that greenhouse gas emissions
for B100 are 74% lower than those from petroleum diesel. More
recently, the California Air Resources Board (CARB) reported
similar values for its life-cycle analysis of biodiesel from
various sources.3
When oilseed plants grow, they take carbon dioxide (CO2) from
the air to make the stems, roots, leaves, and seeds. After the oil
is extracted from the oilseeds, it is converted into biodiesel.
When the biodiesel is burned, CO2 and other emissions are released
and returned to the atmosphere. On balance, most of this emitted
CO2 does not add to the net CO2 concentration in the air because
the next oilseed crop will reuse the CO2 as it grows. A small
fraction of the emitted carbon is fossil derived because of fossil
fuel and chemicals used in farming and in the biodiesel production
process.
Biodiesel Reduces Tailpipe Emissions
Testing to date shows that biodiesel is fully compatible with
the emission control catalysts and filters that dramatically reduce
nitrogen oxides (NOx) and par-ticulate matter (PM) emissions from
new diesel engines (sometimes called NTDEs). The effects are
feedstock neutral for biodiesel. Research is ongoing to determine
whether the current biodiesel specification contains adequate
protection for NTDE emission control catalysts and filters.
NOx emissions have been a concern with older- technology diesel
engines and biodiesel. Some of these concerns about emissions have
been mitigated by replacing older engines with newer engines. CARB
has stated that implementation of NTDEs will eliminate any
fuel-related NOx impacts.4,5 CARB-certified post-2010 model year
vehicles are considered NTDEs.
In late 2015, California set new regulations for the use of
biodiesel in California. Blends above the concen-tration levels
shown in Table 1 must include a NOx-reducing additive.
Exemptions from the requirements in Table 1 are made for the use
of B20 for certain fleets that have more than 90% light- and
medium-duty vehicles or fleets with heavy-duty vehicles with
NOx-neutral technologies and fleets with NTDEs. In addition, the
exemption is in place for retail stations that serve markets where
90% of the fleet is light- and medium-duty vehicles or NTDEs. The
requirement for NOx-reducing additives will sunset when post-2010
model year vehicles comprise 90% of all heavy-duty miles traveled
in the state of California, estimated to be in 2023.6
Off-road diesel engines have long benefited from emissions
reductions using biodiesel blends. With the reduction in the sulfur
content of off-road diesel to the
Table 1. Biodiesel Blend Levels Requiring NOx-reducing
Additives
Type of B100 Time of Year Blend Level
High-saturation feedstock (cetane ≥ 56)
All year B10+
Low-saturation feedstock (cetane < 56)
Low ozone season – November 1 to March 31
B10+
Low-saturation feedstock (cetane < 56)
High ozone season – April 1 to October 31
B5+
3. California Air Resources Board,
arb.ca.gov/fuels/lcfs/lcfs_meetings/040115_pathway_ci_comparison.pdf
accessed November 2, 2015.
4. California Air Resources Board,
arb.ca.gov/fuels/diesel/altdiesel/021314_PublicMeetingPres.pdf,
February 13, 2014.
5. Lammert, M., R. McCormick, P. Sindler, and A. Williams. 2012.
“Effect of B20 and Low Aromatic Diesel on Transit Bus NOx
Emis-sions Over Driving Cycles with a Range of Kinetic Intensity.”
SAE Int. J. Fuels Lubr. 5(3):1345-1359 doi:10.4271/2012-01-1984.
papers.sae.org/2012-01-1984/.
6. California Air Resources Board. 2015. Proposed Regulation on
the Commercialization of Alternative Diesel Fuels, Staff Report:
Initial Statement of Reasons for Proposed Rulemaking.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
5
http://www.arb.ca.gov/fuels/lcfs/lcfs_meetings/040115_pathway_ci_comparison.pdfhttp://www.arb.ca.gov/fuels/lcfs/lcfs_meetings/040115_pathway_ci_comparison.pdfhttp://www.arb.ca.gov/fuels/diesel/altdiesel/021314_PublicMeetingPres.pdfhttp://www.arb.ca.gov/fuels/diesel/altdiesel/021314_PublicMeetingPres.pdfhttp://papers.sae.org/2012-01-1984/http://papers.sae.org/2012-01-1984/
-
same ultra-low levels as on-road diesel, more and more off-road
equipment is using emission control equip-ment. Similar to on-road
engines, biodiesel is fully compatible with these advanced
technologies.
When biodiesel is used in boilers or home heating oil
applications, NOx tends to decrease because the combustion process
is different (open flame for boilers, enclosed cylinder with
high-pressure spray combustion for engines). The NOx reduction seen
with biodiesel blends used in boilers also appears to be
independent of the type of biodiesel used. In blends with heating
oil up to B20, NOx is reduced linearly with increasing biodiesel
content. For every 1% biodiesel added, NOx decreases by 1%. A B20
heating oil fuel will reduce NOx by about 20%.7,8 The sulfur
content of heating oil is steadily being reduced to the same levels
found in on- and off-road diesel fuel. Requirements for reductions
have already been enacted in New York and Con-necticut, with the
rest of New England following suit in coming years.9
Biodiesel and Human Health
An active research area is the impact of biodiesel and its
blends on human health. PM and hydrocarbon emissions from diesel
engines may be toxic and/or carcinogenic. There is a wide range of
literature avail-able on this subject (see for example10, 11, 12).
In 2011, the U.S. Department of Labor Mining Safety and Health
Administration implemented rules for underground mines that limit
worker exposure to diesel PM. The Mining Safety and Health
Administration found that
switching from petroleum diesel fuels to high blend levels of
biodiesel (B50 to B100) significantly reduced PM emissions from
underground diesel vehicles and substantially reduced worker
exposure. However, even low concentrations of biodiesel reduce PM
emissions and provide significant health and compliance benefits
wherever humans receive higher levels of exposure to diesel
exhaust.
Biodiesel Improves Engine Operation
Biodiesel, even in very low concentrations, improves fuel
lubricity and increases the cetane number of the fuel. Diesel
engines depend on the lubricity of the fuel to keep moving parts,
especially fuel pumps and injec-tors, from wearing prematurely. To
address the reduced natural lubricity of ultra-low sulfur diesel,
Specifica-tion ASTM D975 for diesel fuel was modified to add a
lubricity requirement (a maximum wear scar diameter on the
high-frequency reciprocating rig [HFRR] test of 520 microns).
Biodiesel can impart adequate lubricity to diesel fuels with poor
natural lubricity at blend levels as low as 1%.
Biodiesel Is Easy to Use
Finally, one of the biggest benefits to using biodiesel is that
it is easy to use. Blends of B20 or lower require no new equipment
or equipment modifications. B20 can be stored in diesel fuel tanks
and pumped with the same equipment as diesel fuel. B20 does present
a few unique handling and use precautions, but most users can
expect a trouble-free B20 experience.
7. Krishna, C.R. 2003. Biodiesel Blends in Space Heating
Equipment: January 1, 2001 – September 28, 2001, National Renewable
Energy Labora-tory, Golden, CO. NREL/SR-510-33579.
nrel.gov/docs/fy04osti/33579.pdf.
8. Batey, J.E. 2002. Interim report of test results,
Massachusetts Oilheat Council Biodiesel Project.
9. U.S. Energy Information Adminstration. 2013. “Heating Oil
Futures Contract Now Uses Ultra-Low Sulfur Diesel Fuel.”
eia.gov/todayinenergy/detail.cfm?id=11211.
10. Steiner, Sandro, Jan Czerwinski, Pierre Comte, Olga
Popovicheva, Elena Kireeva, Loretta Müller, Norbert Heeb, Andreas
Mayer, Alke Fink, and Barbara Rothen-Rutishauser. 2013. “Comparison
of the Toxicity of Diesel Exhaust Produced by Bio- and Fossil
Diesel Combustion in Human Lung Cells in Vitro.” Atmospheric
Environment 81:380-388.
dx.doi.org/10.1016/j.atmosenv.2013.08.059.
11. Bass, Virginia L., Mette C. Schladweiler, Abraham Nyska,
Ronald F. Thomas, Desinia B. Miller, Todd Krantz, Charly King, M.
Ian Gilmour, Allen D. Ledbetter, Judy E. Richards, and Urmila P.
Kodavanti. 2015. “Comparative Cardiopulmonary Toxicity of Exhausts
from Soy-Based Biofuels and Diesel in Healthy and Hypertensive
Rats.” Inhalation Toxicity 27(11):545-556.
dx.doi.org/10.3109/08958378.2015.1060279.
12. Shvedova, Anna A., Naveena Yanamala, Ashley R. Murray, Elena
R. Kisin, Timur Khaliullin, Meghan K. Hatfield, Alexey V. Tkach, Q.
T. Krantz, David Nash, Charly King, M. Ian Gilmour, and Stephen H.
Gavett. 2013. “Oxidative Stress, Inflammatory Biomarkers, and
Toxicity in Mouse Lung and Liver after Inhalation Exposure to 100%
Biodiesel or Petroleum Diesel Emissions.” Journal of Toxicology and
Environmental Health, Part A 76(15):907-921.
dx.doi.org/10.1080/15287394.2013.825217.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
6
http://www.nrel.gov/docs/fy04osti/33579.pdfhttp://www.eia.gov/todayinenergy/detail.cfm?id=11211http://www.eia.gov/todayinenergy/detail.cfm?id=11211http://dx.doi.org/10.1016/j.atmosenv.2013.08.059http://dx.doi.org/10.3109/08958378.2015.1060279http://dx.doi.org/10.1080/15287394.2013.825217
-
Other Biodiesel Attributes
Lower Energy Density
Neat biodiesel contains about 8% less energy per gallon than
typical No. 2 diesel in the United States, or 12.5% less energy per
pound. The difference between these two measurements is due to the
higher density of biodiesel compared to diesel fuel. All biodiesel,
regardless of its feedstock, provides about the same amount of
energy per gallon or per pound. The energy content of petro-leum
diesel fuel typically varies more widely than that of biodiesel.
However, some reference values are:
Btu/lb. Btu/gal
Typical Diesel No. 2 18,238 129,488 Typical biodiesel (B100)
16,377 119,550 *Btu = British thermal unit
The difference in energy content between petroleum diesel fuel
and biodiesel can be noticeable with B100. For B20, the differences
in power, torque, and fuel economy are 1% to 2%, depending on the
base petro-leum diesel fuel. Most users report little difference in
fuel economy between B20 and No. 2 diesel fuel. Any differences
between B20 and No. 2 diesel fuel are about the same as would be
expected between summer and winter diesel. As the biodiesel blend
level is lowered, dif-ferences in energy content become
proportionally less significant: blends of B5 or lower cause no
noticeable differences in performance compared to No. 2 diesel.
Low-Temperature Operability
In many areas of the country, the cold flow properties of
biodiesel are important. Unlike gasoline, petro-leum diesel and
biodiesel may freeze or gel at common winter temperatures; however,
biodiesel’s cloud point (the temperature at which crystals begin to
form) can be significantly higher than that of petroleum diesel. If
the fuel begins to gel, it can clog filters and eventually become
so thick that it cannot be pumped from the fuel tank to the engine.
However, with proper blending and handling, B20 has been used
successfully all year in the coldest U.S. climates.
Soy biodiesel, for example, has a cloud point of 0°C (32°F). In
contrast, different petroleum diesels have a wide range of cloud
points. Petroleum diesel cloud points can be as low as -45°C
(-49°F) or can be higher, such as -7°C (19°F), depending on time of
year and region of the country. Blending of biodiesel can raise the
cloud point above that of the original diesel fuel, depending on
the starting cloud point of the diesel fuel. For example, a recent
study13 showed that when soy biodiesel was blended into a specially
formulated cold weather diesel fuel (cloud point of -38°C [-36°F])
to make a B20 blend, the cloud point of that blend was -20°C
(-4°F). In very cold climates, this cloud pointmay not be adequate
for wintertime use. To accommo-date biodiesel in cold climates,
low-cloud point petro-leum diesel or low-temperature flow
additives, or both,are necessary. Another option is to reduce the
per-centage of biodiesel in the blend. Generally speaking,with the
same biodiesel and diesel fuel, a B10 will havebetter cold weather
operability properties than a B20.
Stability in Extended Storage
Although biodiesel blends have adequate storage stability for
normal use, special precautions must be taken if they are to be
stored for extended periods. This might occur in seasonal
equipment, like a snow plow or farming equipment, or in the fuel
tank of a backup generator. If the fuel will be stored for more
than a few months, a stability additive is recommended, and
oxidation stability should be measured monthly.
Finally, biodiesel is generally more susceptible than petroleum
diesel to microbial degradation. In the case of spills in the
environment, this is a positive attribute because it biodegrades
more rapidly. However, microbial contamination of fuel storage
tanks can plug dispensers and vehicle fuel filters and cause
vehicles to stall. This is not unheard of for petroleum diesel, but
anecdotal evidence suggests it is a greater problem for biodiesel
blends. The best way to deal with this issue (for both petroleum
diesel and biodiesel) is adequate fuel storage tank housekeeping
and monitoring, especially minimiz-ing water in contact with the
fuel. Water bottoms must be removed from tanks, and standing tanks
should be sampled and tested for microbial contamination.
13. Coordinating Research Council. 2006. Biodiesel Blend
Low-Temperature Performance Validation.
crcao.com/reports/recentstudies2008/DP-2a-07/CRC%20650.pdf.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
7
http://astm.orghttp://astm.org
-
This section describes the basic considerations for handling and
blending B100. In the United States, it is equally common to handle
B99 and B99.9 blends. The considerations in this section also apply
to B99 and B99.9, as these fuel blends often qualify for a tax
credit for biodiesel blending. At the time of this writing (2016),
a tax credit for blending biodiesel is available through 2016. The
storage and handling procedures for B100 are very different than
for B20 and lower biodiesel blends and vary significantly from
those for diesel fuel. Table 2 lists some of the physical and
chemical properties of B100 and petroleum diesel. Using B20 and
lower blends significantly reduces or eliminates the effects of
these property differences for use as an engine fuel. However,
because many distributors store and handle B100 before blending, a
good understanding of B100 properties is valuable. Several
significant attributes specific to B100 that should be considered
when handling, storing, and using it are described below.
• B100 is a good solvent. It may loosen or dissolvevarnish and
sediments in fuel tanks and fuelingsystems left by conventional
diesel over time. Ifa system contains sediments, the tanks and
fuelsystem should be cleaned before B100 is handled orused. A good
indication that B100 is cleaning thetank is an initial increase in
filter plugging. Overtime, filter change intervals should return to
normal.This should not be an issue for B20 or lower blends.
• B100 gels at higher temperatures than mostdiesel fuel. This
must be taken into account ifhandling or using B100, especially in
abovegroundstorage tanks (ASTs). The temperature where B100starts
to gel will vary with the feedstock and canrange from 0°C to 15°C
(32°F to 60°F) or higher, soheated fuel lines and tanks may be
needed duringwinter, even in moderate climates. As B100 beginsto
gel, the viscosity rises to much higher levels thanmost diesel
fuel, which can increase the stress on
Biodiesel (B100)
Table 2. Select Properties of Typical No. 2 Diesel and Biodiesel
Fuels
Fuel Property Diesel Biodiesel, No. 1-B grade
Fuel standard ASTM D975 ASTM D6751
Higher heating value, Btu/gal Lower heating value, Btu/gal
~138,490 ~129,488
~127,960 ~119,550
Kinematic viscosity, @ 40°C (104°F) 1.3 – 4.1 4.0 – 6.0
Specific gravity @ 15.5°C (60°F) 0.85 0.88
Density, lb/gal @ 15.5°C (60°F) 7.1 7.3
Carbon, wt % 87 77
Hydrogen, wt % 13 12
Oxygen, by dif. wt % 0 11
Sulfur, wt % (parts per million [ppm]) 0.0015 max. (15 ppm max.)
0.0 – 0.0015 (0 – 15 ppm)
Boiling point, °C (°F) 180 – 340 (356 – 644) 315 – 350 (599 –
662)
Flash point, °C (°F) 60 – 80 (140 – 176) 100 – 170 (212 –
338)
Cloud point, °C (°F) -35 – 5 (-31 – 41) -3 – 15 (26 – 59)
Pour point, °C (°F) -35 – -15 (-31 to 5) -5 – 10 (23 – 50)
Cetane number 40 – 55 47 – 65
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
8
-
pumps. The high cloud point of B100 makes its use challenging in
colder climates.
• B100 is not compatible with some hoses andgaskets. B100 may
soften and degrade certain typesof rubber compounds used for hoses
and gaskets(buna-N, nitrile, natural rubber) and may causethem to
leak and degrade to the point where theycrumble and become useless.
For bulk handling ofB100, seals, gaskets, and hoses must be
compatiblewith B100. (See Appendix C for information aboutmaterial
compatibility.) Using B100 in an engineconstructed with
incompatible materials can causea fuel spill on a hot engine, ruin
a fuel pump, orclog a filter as the hose material gradually
erodes.Use extreme care to ensure that any part of thefuel system
that touches the fuel is compatible withB100. Some systems may
employ certain grades ofViton, which are biodiesel-resistant
materials, butmany do not, because these materials are
usuallyslightly more expensive.
• B100 is not compatible with some metals andplastics. Biodiesel
will degrade and form high sedi-ment levels if contacted for long
periods by copperor copper-containing metals (brass, bronze) orwith
lead, tin, or zinc (galvanized surfaces). Thesehigh sediment levels
may clog filters. B100 may alsopermeate some common plastics
(polyethylene,polypropylene) over time, so these should not beused
for storing B100.
B100 Quality Specification
The specification for biodiesel (B100) is frequently updated,
and as of this writing the most current version is D6751-15cε1,
summarized in Table 3. For the most up-to-date version of the
specification, check the ASTM website (astm.org).
In 2012, a new grade of B100 was added to the D6751
specification. This new grade is referred to as the No. 1-B grade
and is a special-purpose grade of biodieselmeeting more stringent
purity requirements intendedto provide better low-temperature
performance. Mostbiodiesel produced at the time of publication is
No. 1-Bgrade. This grade may be required in certain applica-tions,
but it is up to the customer to select the propergrade of biodiesel
for their application.
Specification D6751 is intended to ensure the quality of
biodiesel to be used as a blend stock in middle distil-lates, like
diesel fuel and heating oil, at 20% and lower levels. Any biodiesel
used in the United States should meet ASTM D6751 before blending.
ASTM D6751 is based on the physical and chemical properties needed
for safe and satisfactory diesel engine and boiler opera-tions. It
is not based on the specific raw materials or the manufacturing
process used to produce the biodiesel. The finished blend stock
must meet the properties specified in Table 3 as well as the
following definition from D6751:
Table 3. Requirements for Biodiesel (B100) Blend Stock as Listed
in ASTM D6751-15cε1
Property Test Method
Grade No. 1-B, S15
Grade No. 1-B, S500
Grade No. 2-B, S15
Grade No. 2-B, S500
Sulfur, % mass (ppm), max D5453 0.0015 (15) 0.05 (500) 0.0015
(15) 0.050 (500)
Cold soak filterability, s, max D7501 200 200 360 360
Monoglycerides, % mass, max D6584 0.40 0.40 – –
Requirements for All Grades
Calcium and magnesium, combined, ppm, max
EN14538 5
Flash point (closed cup), °C, min D93 93
Alcohol Control One of the following shall be met:
1. Methanol Content, mass %, max2. Flash Point, °C, min
EN14110D93
0.2130
Table 3 continued on next page
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
9
http://www.astm.org
-
“Biodiesel, noun, a fuel comprised of mono-alkyl esters of long
chain fatty acids derived from vegetable oils or animal fats,
designated B100.”
This specification was never intended to be applied to B100 to
be used as a neat fuel. However, buyers and sellers are encouraged
to use ASTM D6751 for the com-mercial trading of biodiesel (B100)
for blending. Other arrangements or specifications can be legally
used if the buyer and seller agree as long as they meet perti-nent
local, state, and federal regulations (EPA sulfur limits,
Occupational Safety and Health Administration [OSHA] safety limits
on flash point, etc.). However, B100 must meet the requirements of
D6751 for blends to be legal fuels under the Clean Air Act fuel
registra-tion requirements and to be a legal blending component
under many state regulations.
The intent of each quality requirement in Table 3 is described
here:
• High levels of Group I and II metals. Sodium (Na),potassium
(K), calcium (Ca), and magnesium (Mg)can cause deposits to form,
catalyze undesiredside reactions, and poison emission control
equip-ment. The Group I and II metals are limited as thecombination
of metals in each category, Na+K andCa+Mg. The specification upper
limit is 5 parts permillion (ppm), combined, for each pair of
metals.Research is ongoing to determine whether thesemetals limits
are adequate for protection of NTDEemission control catalysts and
filters.
• Flash point. A minimum flash point for dieselfuel is required
for fire safety. B100’s flash point isrequired to be at least 93°C
(200°F) to ensure all the
Table 3 (cont.). Requirements for Biodiesel (B100) Blend Stock
as Listed in ASTM D6751-15cε1
Property Test Method
Grade No. 1-B, S15
Grade No. 1-B, S500
Grade No. 2-B, S15
Grade No. 2-B, S500
Requirements for All Grades
Water and sediment, % volume, max D2709 0.050
Kinematic viscosity, mm2/s, 40°C D445 1.9 – 6.0
Sulfated ash, % mass, max D874 0.020
Copper strip corrosion, max D130 No. 3
Cetane number, min D613 47
Cloud point, °C D2500 Report
Carbon residue, % mass, max D4530 0.050
Acid number, mg KOH/g, max D664 0.50
Free glycerin, % mass, max D6584 0.020
Total glycerin, %mass, max D6584 0.240
Phosphorus content, % mass, max D4951 0.001
Distillation temperature, 90% recov-ered, °C, max
D1160 360
Sodium and potassium, combined, ppm, max
EN14538 5
Oxidation stability, hr, min EN15751 3
Note: Reprinted with permission of ASTM.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
10
-
alcohol from production is removed; it is classified as
nonhazardous under the National Fire Protec-tion Association
code.
• Alcohol. It is critical to ensure that the manufac-turer has
removed excess alcohol (typically metha-nol) used in the
manufacturing process. Residualmethanol in the fuel is a safety
issue, because evenvery small amounts dramatically reduce the
flashpoint, can affect fuel pumps, seals, and elastomers,and can
result in poor engine combustion proper-ties. The intent of the
alcohol control requirementis to limit volatile alcohols to less
than 0.2 percentby weight (wt %). This can be accomplished
bymeeting a higher flash point requirement of 130°C(266°F) or by
measuring methanol content by gaschromatography.
• Water and sediment. This refers to free water drop-lets and
sediment particles suspended in the B100.The allowable level for
B100 is set at the same levelas for conventional diesel fuel. Poor
drying tech-niques during manufacturing or contact with exces-sive
water during transport or storage can causeB100 to be out of
specification for water content.Excess water can lead to corrosion
and provides anenvironment for microorganisms. Fuel oxidationcan
also raise sediment levels, so this test can beused in conjunction
with acid number, oxidationstability, and viscosity to determine if
fuels haveoxidized too much during storage.
• Viscosity. A minimum viscosity is required forsome engines
because of the potential for powerloss caused by injection pump and
injector leakage.This is not an issue for B100, and the minimumis
set at the same level as for petroleum diesel.The maximum viscosity
is limited by the designof engine fuel injection systems. Higher
viscosityfuels can cause poor fuel combustion that leads todeposit
formation as well as higher in-cylinder pen-etration of the fuel
spray, which can result in ele-vated engine oil dilution with fuel.
The maximumallowable viscosity in ASTM D975 for No. 2 dieselis 4.1
mm2/s at 40°C (104°F). ASTM D6751 allowsfor slightly higher
viscosity than D975, primar-ily because the normal viscosity of
B100 is slightlyhigher than that of diesel fuel. Biodiesel blends
of20 vol% or lower should have viscosities between 1.9and 4.1
mm2/s, within the range allowed by D975.
• Sulfated ash. This test measures the amount ofresidual alkali
catalyst in the biodiesel as well asany other ash-forming compounds
that could con-tribute to injector deposits or fuel system
fouling.
• Sulfur. This is limited to 15 ppm to reduce sulfateand
sulfuric acid pollutant emissions and to protectexhaust catalyst
systems on NTDEs. Biodieselgenerally contains less than 15 ppm
sulfur. The testfor sulfur in fuel (ASTM D5453) should be usedfor
accurate results instead of D2622, which willprovide falsely high
results caused by test interfer-ence with the oxygen in the
biodiesel.
• Copper strip corrosion. This test is used to indicatepotential
difficulties with copper and bronze fuelsystem components. The
requirements for B100and conventional diesel are identical, and
biodieselmeeting other D6751 specifications always passesthis test.
Copper and bronze may not corrode in thepresence of biodiesel, but
prolonged contact withthese catalysts can degrade the fuel and
cause sedi-ment to form.
• Cetane number. An adequate cetane number isrequired for good
engine performance. Conven-tional diesel must have a cetane number
of at least40 in the United States. Higher cetane numbers
helpensure good cold start properties and minimize theformation of
white smoke. The ASTM minimumlimit for B100 cetane number is set at
47 becausethis is the level identified for “Premium DieselFuel” by
the National Conference of Weights andMeasures. Also, a 47 cetane
number has been thelowest cetane number found in U.S. biodiesel,
froma wide array of diverse feedstocks. The cetane index(ASTM D976)
is not an accurate predictor of cetanenumber for biodiesel or
biodiesel blends because itis based on a calculation that uses
specific gravityand distillation curve, both of which are
differentfor biodiesel than for petroleum diesel.
• Cloud point is the most commonly used measureof
low-temperature operability. Fuels are generallyexpected to operate
at temperatures as low as theircloud point. The cloud point of B100
is typicallyhigher than the cloud point of conventional dieselfuel.
Cloud point must be reported for biodiesel.Low-temperature
properties and strategies forensuring good low-temperature
performance ofbiodiesel blends are discussed in more detail inlater
sections.
• Carbon residue measures the carbon-depositingtendency of a
fuel and is an approximation of thetendency for carbon deposits to
form in an engine.For conventional diesel fuel, the carbon residue
ismeasured on the 10% distillation residue. BecauseB100 boils
entirely at the high end of the diesel fuelrange and in a very
narrow temperature range, it is
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
11
-
difficult to leave only a 10% residue when distilling biodiesel.
So biodiesel carbon residue specifies that the entire biodiesel
sample be used rather than the 10% distilled residue.
• Acid number for biodiesel is primarily an indicatorof free
fatty acids (natural degradation productsof fats and oils or a
component of some biodieselfeedstocks) and can be elevated if a
fuel is notproperly manufactured or has undergone
oxidativedegradation. Acid numbers higher than 0.50 mil-ligram
potassium hydroxide per gram (mg KOH/g)have been associated with
fuel system deposits andreduced life of fuel pumps and filters.
• Free and total glycerin numbers measures theamount of
unconverted or partially converted fats/oils and by-product
glycerin in the B100. Incom-plete conversion of the fats and oils
into biodieselcan lead to high total glycerin from elevated
mono-,di-, and tri-glycerides. Incomplete removal ofglycerin can
lead to high free and total glycerin. Ifthe glycerides are too
high, the storage tank, fuelsystem, and engine can be contaminated.
Fuelsthat exceed these limits are highly likely to plugdispenser
and/or vehicle filters and cause otherproblems. One of the major
shortcomings of theD6584 gas chromatograph method is its
sensitivityto diesel fuel. Diesel fuel components overwhelmthe
column used in the gas chromatograph, makingaccurate determination
of glycerin and glycer-ides difficult or impossible, and may damage
thecolumn. Thus, many laboratories are unable todetermine free and
total glycerin by this method insamples with even small amounts of
diesel fuel.
• Phosphorus content is limited to 10 ppm maximumin biodiesel
because it can damage emission controlsystems. Phosphorus above 10
ppm can be presentin some plant oils and recycled greases. At
thistime, biodiesel produced in the United States gener-ally has
phosphorus levels of about 1 ppm.
• The T90 distillation is the temperature where 90%of the fuel
has distilled. The specification wasincorporated to ensure that
fuels have not beencontaminated with high boiling materials suchas
used motor oil or triglycerides. B100 exhibits aboiling point
rather than a distillation curve. Thefatty acids from which
biodiesel are produced aremainly straight chains with 16 to 18
carbons thathave similar boiling point temperatures. The
atmo-spheric boiling point range of biodiesel is generally330°C to
357°C (626°F to 675°F).
• Oxidation stability. Biodiesel can oxidize duringstorage and
handling, leading to the formation ofperoxides, acids, gums, and
deposits. The minimumoxidation stability requirement is intended to
ensurethe storage stability of B100 and biodiesel blends inclean
tanks.
• Cold soak filterability was added in 2008 inresponse to data
indicating that some B100 could,in blends with petroleum diesel of
up to 20%, formprecipitates above the cloud point. B100 meeting
thecold soak filterability requirements does not formthese
precipitates. This, along with cloud point, isneeded to predict
low-temperature operability.
• No. 1-B grade. The No. 1-B grade has year-roundlimits on cold
soak filterability and monoglycer-ides. These limits ensure that
trace componentsin biodiesel are minimized, while not requiringthe
measurement of many different compoundsthat may or may not be
present in biodiesel. Inparticular, the limit on monoglycerides
limits thesaturated monoglyceride (SMG) content of thebiodiesel.
The percent of SMG in a B100 will bedetermined by the percent of
saturated FAME.For example, if a B100 is 30% saturated FAME,the
monoglyceride in the B100 will containapproximately 30% SMG.
Specification D6751 also includes the following work-manship
statement:
“The biodiesel fuel shall be visually free of undissolved water,
sediment, and suspended matter.”
Variation in Biodiesel Properties
As with petroleum-based fuels, the ASTM specification for
biodiesel allows for a variety of feedstocks and pro-cesses to be
used in its production. In today’s market, biodiesel is most
commonly a blend of B100 from two or more feedstocks. Many
producers use feedstocks from a variety of sources to obtain B100
with desired proper-ties and to improve production economics.
The specification prescribes a largely feedstock-neutral,
performance-based set of requirements that ensure the B100 is fit
to be used in diesel engines. Biodiesel can be produced
commercially from a variety of oils and fats:
• Animal fats. Tallows, lard, choice white grease,yellow grease,
poultry fats, and fish oils
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
12
-
• Plant oils. Soy, corn, canola, sunflower, rapeseed,cottonseed,
corn
• Recycled greases. Used cooking oils and restau-rant frying
oils.
Biodiesel can also be made from other oils, fats, and recycled
oils such as mustard, palm, coconut, peanut, olive, sesame, and
safflower oils, trap greases, and even oils produced from algae,
fungi, bacteria, molds, and yeast. Some properties of finished
biodiesel such as cetane number, cloud point, and stability depend
heavily on the feedstock.
Compared to the chemistry of diesel fuel, which con-tains
hundreds of compounds, the chemistries of dif-ferent fats and oils
typically used for biodiesel are very similar. Each fat or oil
molecule is made up of a glyc-erin backbone of three carbons, and
on each carbon is attached a long-chain fatty acid that reacts with
metha-nol to make the methyl ester, or biodiesel. The glycerin
backbone is turned into glycerin and sold as a co-product of
biodiesel manufacturing. Currently, the fats and oils used to make
commercial biodiesel contain 10 common types of fatty acids that
have 12 to 22 carbons, more than 90% of which are 16 to 18 carbons.
Some of these chains are saturated, some are monounsaturated, and
others are polyunsaturated. Within the limits of the
specifications, the differing levels of saturation can affect some
biodiesel fuel properties.
Each feedstock is set apart from the others because it is made
of different proportions of saturated, monoun-saturated, and
polyunsaturated fatty acids (Figure 2).
In general, saturated FAME have high cetane numbers and cloud
points and are more stable. As unsaturation increases (i.e., the
number of double bonds increases), the cetane number and cloud
point decrease, as does the natural stability of the FAME. The
cetane number and stability are easily treated with conventional
addi-tives, while the cloud point is more difficult to treat. The
length of the fatty acids also has an impact on the biodiesel
properties. For example, coconut methyl esters are highly
saturated, and the shorter chain length results in a cloud point of
-5°C. While it is useful to understand the relationship between
saturation and biodiesel proper-ties, users are encouraged to base
purchase decisions on measured fuel properties.
As with conventional diesel fuel, the best type of biodiesel for
your applications will be based on several factors. A No. 2
petroleum diesel fuel with a cetane number of 50 and a cloud point
of -3°C (26°F) may be suitable for December in Texas, but a No. 1
petroleum diesel with a cetane number of 42 and a cloud point of
-29°C (-20°F) may be best for December in Minnesota. The
consider-ations and tradeoffs for biodiesel use are like those made
for petroleum diesel fuel. The following data provide more detail
about B100 properties and considerations.
Canola
Sa�ower
Sunflower
Corn
Olive
Soybean
Peanut
Cottonseed
Yellow Grease
Lard
Beef Tallow
Palm
Coconut
0 20% 40% 60% 80%10% 30% 50% 70% 90% 100%
Saturated Monounsaturated Polyunsaturated
Figure 2. Composition of various biodiesel feedstocks in order
of increasing saturated fatty acid content
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
13
-
Energy Content
With conventional diesel fuels, the inherent energy content of
the fuel is the largest factor affecting the fuel economy, torque,
and horsepower delivered by the fuel. The energy content of
conventional diesel can vary up to 15% from supplier to supplier
and from summer to winter. This variability is due to changes in
its composi-tion that are determined by the petroleum feedstock, as
well as refining and blending practices to produce finished diesel
fuels. No. 2 diesel fuel usually has higher energy content than No.
1 diesel fuel, with blend values somewhere in between.
With B100, the refining (esterification or transesteri-fication)
process and blending of B100 from different feedstocks has no
significant effect on energy content. The energy content of B100
varies little because the energy content of the fats and oils used
in biodiesel production is highly similar. Therefore, B100 made
from most of the common feedstocks will have the same fuel economy,
power, and torque when burned in an engine. Compared to most No. 2
diesel fuel in the United States, B100 has a slightly lower energy
content (12.5% per pound or 8% per gallon). Typical No. 2 diesel
fuel has an energy content of around 18,200 Btu/lb. Losses in
power, torque, and fuel economy would be expected to be
proportional to the difference in energy content, although any
differences may be too small to notice. The energy content of
biodiesel blends and diesel fuel is proportional to the amount of
biodiesel in the blend and the heating value of the biodiesel and
diesel fuel used to make the blend. For example, B20 users
experi-ence a nearly 1% loss in fuel economy on average, which may
not be noticeable to the driver, and rarely report changes in
torque or power.
Low-Temperature Properties
The low-temperature properties of biodiesel and con-ventional
petroleum diesel are extremely important. Unlike gasoline,
petroleum diesel and biodiesel can freeze or gel as the temperature
drops. Different diesel fuel formulations are sold during the
winter in many climates. If the fuel begins to gel, it can clog
filters on dispensing equipment and may eventually become too thick
to pump. B100 is commonly stored in heated aboveground tanks for
blending in winter. Important low-temperature performance metrics
for handling and blending of B100 are:
• Cloud point. The temperature at which smallsolid crystals are
first visually observed as the fuelis systematically cooled. The
crystals formed inB100 are not like the crystals formed in diesel
fueland may behave differently in the fuel. Below thefuel’s cloud
point, these crystals might plug filtersor could drop to the bottom
of a storage tank.However, fuels can usually be pumped at
tempera-tures below the cloud point.
• Pour point. The temperature at which the fuelcontains so many
agglomerated crystals it is essen-tially a gel and will no longer
flow. Distributors andblenders use pour point as an indicator of
whetherthe fuel can be pumped, even if it would not be suit-able
for use without heating or taking other steps.
These guidelines should be followed for storing bio-diesel
(B100) in winter:
• B100 should be stored at temperatures at least2.5°C to 5°C
(5°F to 10°F) higher than the cloudpoint. Because the cloud point
of the B100 varies,the storage temperature will not be the same
forall biodiesels.
• B100 from all but the highest cloud point feed-stocks such as
tallow or palm oil can be storedunderground in most cold climates
without addi-tional considerations because underground
storagetemperatures are normally above 7°C (45°F).Aboveground
storage and handling systems shouldbe protected with insulation,
agitation, heatingsystems, or other measures if temperatures
regu-larly fall below the cloud point. This precautionincludes
piping, tanks, and pumping equipment.
The cloud point of B100 starts around -1°C to 0°C (30°F to 32°F)
and can go as high as 20°C (68°F) or higher for biodiesel from
highly saturated feedstocks (see Table 4 on next page). The pour
point of B100 is usually only a few degrees lower than the cloud
point, so once bio-diesel begins to freeze, gelling can occur
rapidly if the temperature drops only a few degrees further.
B100 tanks and fuel lines should be designed for the cold flow
properties of the biodiesel being used and the local climate. Fuel
pumps, lines, and dispensers must be protected from cold and wind
chill with properly approved heating and insulating equipment. Fuel
in aboveground tanks should be heated to 2.5°C to 5°C (5°F to 10°F)
above the fuel cloud point.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
14
-
In some rare cases, as B100 gets colder, impurities like SMGs
may precipitate out of solution. SMGs exhibit an interesting
behavior known as polymorphism,15 where the crystal form changes
after precipitation. When SMGs first precipitate out of solution,
they are in a less stable and more soluble form. Over time, the SMG
crys-tals can transform into a more stable and less soluble form.
These highly stable SMG crystals are difficult to bring back into
solution, and the B100 must be heated well with adequate
mixing.
Most of the time, once crystals form, they will generally go
back into solution as the fuel warms. However, that process can be
slow if the fuel is heated only slightly above the cloud point.
Crystals formed in biodiesel or diesel fuel can drift to the bottom
of the tank and begin to build up. Slow agitation can prevent
crystals from building up on the tank bottom or, once present in
the fuel, can help to bring the crystals back into liquid form. If
B100 has gelled completely, the B100 should be heated to 38°C to
43°C (100°F to 110°F) to dissolve the most highly saturated
biodiesel components if the fuel needs to be used immediately.
Lower temperatures can be used if there is more time to allow the
biodiesel to liquefy.
The low-temperature performance of B100 cannot be effectively
managed with current cold flow additives, as can petroleum diesel
and biodiesel blends. The level of saturated compounds in B100 is
too high for most additives to be effective. Cold flow additives
have been used much more successfully with biodiesel blends. You
should work directly with the additive manufacturers on this
issue.
Cetane Number
Cetane number is a measure of the ignition delay (the time from
fuel injection into the combustion chamber to ignition); higher
cetane numbers are believed to provide easier starting and quieter
operation. ASTM D6751 for biodiesel requires a minimum cetane
number of 47; the cetane number required of petroleum diesel fuel
is 40. B100 produced from highly saturated feedstocks can have a
cetane number of 60 or higher. Figure 3 shows the cetane numbers of
various biodiesel samples and compares them to diesel cetane
numbers. While it is interesting to know the cetane numbers of
biodiesels from different feedstock oils, biodiesel is most
com-monly a blend from two or more feedstocks. Thus, buyers should
focus on measured fuel properties rather than trying to determine
the feedstock source.
Table 4. Cold Flow Data for Various B100s14
Degree of saturation
B100 Cloud Point ASTM D2500
B100 Pour Point ASTM D97
°F °C °F °C
Low 26 -3 25 -4
32 0 25 -4
Mid
46 8 43 6
56 13 55 13
61 16 59 15
High 66 19 60 16
14. Kinast, J.A. 2003. Production of Biodiesels from Multiple
Feedstocks and Properties of Biodiesels and Biodiesel/Diesel
Blends: Final Report; Report 1 in a Series of 6, p. 13. National
Renewable Energy Laboratory, Golden, CO. NREL/SR-510-31460.
nrel.gov/docs/fy03osti/31460.pdf.
15. Chupka, G.M., Yanowitz, J., Chiu, G., Alleman, T.L., and
McCormick, R.L., “Effect of Saturated Monoglyceride Polymorphism on
Low-Tempera-ture Performance of Biodiesel.” Energy and Fuels, 2011
25(1), 398=405, doi: 10.1021/ef1013743.
EPA Highway Diesel
CARB Diesel
Lard
Edible Tallow
Inedible Tallow
Yellow Grease 1
Yellow Grease 2
Canola
Soy
0 10 20 30
Cetane Number40 50 60 70
Figure 3. Cetane numbers of two petroleum diesels and several
biodiesels
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
15
http://www.nrel.gov/docs/fy03osti/31460.pdf
-
Transport and Storage
Stability
Stability can refer to two issues for fuels: long-term storage
stability or aging and stability at elevated temperatures and/or
pressures as the fuel is recirculated through an engine’s fuel
system. For petroleum diesel, long-term storage stability is
commonly referred to as oxidative stability. Thermal stability is
the common term for the stability of fuels at elevated fuel system
temperatures. For B100, storage stability is the para-mount
concern; thus, D6751 includes an oxidation stability
requirement.
The oxidation stability test, EN15751 (also referred to as the
Oil Stability Index or the Rancimat test), involves heating a
specified quantity of B100 to 110°C (230°F) while air is bubbled
through the sample at a controlled flow rate. After bubbling
through the B100, the air bubbles through a water bath that
collects volatile acids formed by oxidation of the biodiesel. A
conductivity meter is used to monitor the water. A stable B100 can
go for many hours under these conditions without forming volatile
oxidation products. This period of time, before oxidation products
form, is called the induction time or induction period. The
stability requirement in D6751 is that the B100 have a minimum
three-hour induction time. Because this requirement applies at the
time of blending, many biodiesel producers make B100 with higher
induction times.
In biodiesel, fuel aging and oxidation can lead to high acid
numbers, high viscosity, and the formation of gums and sediments
that clog filters. If the oxidation stabil-ity, acid number, or
viscosity measurements exceed the limits in ASTM D6751, the B100 is
degraded to the point where it is out of specification and should
not be used. Biodiesel with high oxidation stability (longer
induction time) will generally take longer than biodiesel with low
oxidation stability to reach an out-of-specifica-tion condition.
Monitoring the induction time and acid number of B100 over time can
provide an indication of oxidation. B100 should be tested at
receipt to ensure it is within specification. If the biodiesel will
be stored prior to blending, the induction time and acid number
should be monitored at regular intervals to ensure the biodiesel is
not oxidizing.
In some cases, deposits from the cleaning or solvent effect of
B100 have been confused with gums and sediments that could form in
storage as the B100 ages. Although sediment can clog a filter in
either case, care
should be taken to make sure the reason for the clog-ging is
properly identified. For example, if oxidation stability and acid
number are within specification, sediments are most likely due to
the cleaning effect and not to aging or oxidation.
Guidelines to help identify biodiesel and storage conditions
that will provide the highest levels of stability follow:
• The higher the level of unsaturation, the more likelythat the
B100 will oxidize. Saturated fatty acidesters are fairly stable,
and each time the level ofunsaturation increases (for example, from
monoun-saturated to polyunsaturated), the stability of thefuel
decreases exponentially. The points of unsatu-ration on the
biodiesel molecules can react withoxygen, forming peroxides that
break down intoacids, sediments, and gums.
• Heat and sunlight will accelerate this process.
• Certain metals such as iron, rust, copper, brass,bronze, lead,
tin, and zinc will accelerate thedegradation process and form even
higher levels ofsediment. B100 should not be stored in systems
thatcontain these metals.
• Some types of feedstock processing and biodieselprocessing can
remove natural antioxidants,potentially lessening inherent
stability. Plant oilsand fats are produced with natural
antioxidants—nature’s way of protecting the oil from
degradation.Bleaching, deodorizing, or distilling oils and
fats,either before or as part of the biodiesel process, canremove
these natural antioxidants.
• Antioxidants, whether natural or incorporated asadditives, can
significantly increase the storage lifeor stability of B100.
• Keeping oxygen from the biodiesel reduces oreliminates fuel
oxidation and increases storagelife. Commercially, this is done by
using a nitrogenblanket on storage tanks or storing biodiesel
insealed drums or totes with minimal headspace.
The ASTM D4625 test is used to simulate storage at ambient
temperature, roughly 21°C (70°F). The test is accelerated by a
factor of 4 for petroleum fuels, that is, one week of storage at
D4625 conditions (43°C or 110°F, open to air) simulates one month
of storage at 21°C (70°F). This acceleration factor has not been
validated
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
16
-
for B100, but it is still a useful guide. ASTM D4625 data (see
Figure 4)16 indicate that B100 will lose oxida-tion stability over
time under these storage conditions. Higher initial induction
period values can provide longer storage time before biodiesel goes
out of specifi-cation. Figure 4 also shows that, as the oxidation
stabil-ity is reduced to near zero, the material will oxidize due
to a loss of “oxidation reserve.” This is evident in the increase
in peroxide values. Acid numbers remain relatively constant until
peroxide values become very high. Once sufficient peroxides have
formed, the acid number increases rapidly due to peroxide
degradation. Measurement of insoluble material in these B100s was
not statistically significant during D4625 storage for 13 weeks
(simulating 1 year of storage); however, highly oxidized
biodiesels—having acid numbers well above the D6751 limit of 0.5 mg
KOH/g—have historically been shown to form insoluble
materials.17
B100 should not be stored longer than four months unless it has
been treated with synthetic antioxidants and has an oxidation
stability of 6 hours or longer. Non-oxidizing storage conditions in
containers with little head space or under a nitrogen blanket will
also be helpful. In fact, when B100 is being stored longer than
about two months, it should be tested for oxidation sta-bility
every two weeks. One of the best ways to stabilize biodiesel is to
blend it with petroleum diesel.
Microbial Contamination
Biocides are recommended for fuels wherever biologi-cal growth
in the fuel has been a problem. If biological contamination occurs,
water contamination should be suspected and will need to be
controlled because the aerobic fungus, bacteria, and yeast
hydrocarbon-utilizing microorganisms usually grow at the fuel-water
interface. Anaerobic colonies, which usually reduce sulfur, can be
active in sediments on tank surfaces and cause corrosion. Because
the biocides work in the water phase, products that are used with
diesel fuels work equally well with biodiesel.
Figure 4. ASTM D4625 long-term storage stability for B100
samples having a range of initial induction periods
20
15
10
5
00 2 4 6
Weeks at 43°C
Indu
ctio
n Pe
riod,
hr
8 10 12 14 16
1.04.89.27.58.417.73.73.20.5 mg KOH/g
0.8
0.6
0.4
0.2
00 2 4 6
Weeks at 43°C
Aci
d N
umbe
r, m
g KO
H/g
8 10 12 14 16
4.89.27.58.417.73.73.2
3,000
2,500
2,000
1,500
1,000
500
00 2 4 6
Weeks at 43°C
Pero
xide
Val
ue, m
g/kg
8 10 12 14 16
16. Christensen, E., and R.L. McCormick. 2014. “Long-Term
Storage Stability of Biodiesel and Biodiesel Blends,” Fuel
Processing Technology 128:339–348.
17. McCormick, R.L., and S.R. Westbrook 2010. “Storage Stability
of Biodiesel and Biodiesel Blends.” Energy & Fuels
24(1):690–698.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
17
-
Corrosion can also be the result of impurities like water, free
glycerin, free fatty acids, or the sodium or potas-sium used in
biodiesel processing. Oxidized biodiesel and biodiesel blends can
contain organic acids and other compounds that can significantly
accelerate elas-tomer degradation. Ensuring that all biodiesel
meets the specifications when brought on site and in storage can
minimize corrosion risks.
If your equipment is not compatible with B100, the materials
should be replaced with materials such as Teflon, Viton,
fluorinated plastics, or nylon. You should consult B100 suppliers
and equipment vendors to determine material compatibility, and ask
B100 vendors in other regions what problems they may have
experi-enced and what kind of replacement materials they are using.
It is advisable to set up a monitoring program to visually inspect
the equipment once a month for leaks, seeps, and seal
decomposition.
Transport
As with petroleum diesel, B100 must be transported in a way that
does not lead to contamination. The following procedures are
recommended for trucks and railcars and are used by distributors
and transporters of diesel fuel.
• Ensure that trucks and railcars are constructed ofaluminum,
carbon steel, or stainless steel.
• Ensure proper inspection or washout (washoutcertificate)
before loading.
• Check for previous load carried and residualmaterial.
Generally, only diesel fuel or biodiesel isacceptable as a
residual. If the vessel has not gonethrough a washout, some
residuals, including foodproducts or raw plant oils, gasoline or
lubricants,may not be acceptable.
• Ensure there is no residual water in the tank.
• Check that hoses and seals are clean and made frommaterials
that are compatible with B100.
• Determine the need for insulation or a method toheat truck or
rail car contents if shipping duringcold weather. B100 is
challenging to ship in coldweather. In the winter, most B100 is
shipped in oneof the following ways:
- Hot (or at least warm) in trucks for immediatedelivery at 27°C
to 54°C (80°F to 130°F).
Cleaning Effect
Methyl esters have been used as low volatile organic compound
cleaners and solvents for decades. Methyl esters make excellent
parts cleaners, and several com-panies offer methyl esters as a low
volatile organic compound, nontoxic replacement for the volatile
solvents used in parts washers. B100 will dissolve the accumulated
sediments in diesel storage and engine fuel tanks. These dissolved
sediments can plug filters. If this happens, it can cause injector
deposits and even fuel injector failure. If you plan to use or
store B100 for the first time, clean the tanks and any parts in the
fuel system where sediments or deposits may occur before filling
with B100.
The level of cleaning depends on the amount of sedi-ment in the
system (if the system is free of sediment, there should be no
effect) as well as the biodiesel blend level—the higher the blend
level, the greater the clean-ing potential. The cleaning effect is
much greater with B100 and blends with 35% or more biodiesel,
compared to B20 and lower blends.
Biodiesel spills should be immediately cleaned up because
biodiesel can damage some types of body and engine paint. Biodiesel
can also remove decals from tanks or vehicles near the fueling
areas. All materials that are used to absorb biodiesel spills
should be consid-ered combustible and stored in a safety can.
Materials Compatibility
B100 will degrade, soften, or seep through some hoses, gaskets,
seals, elastomers, glues, and plastics with prolonged exposure.
Nitrile rubber compounds, poly-propylene, polyvinyl, and Tygon
materials are particu-larly vulnerable to B100. Before handling or
using B100, ask the equipment vendor or OEM if the equipment is
suitable for B100 or biodiesel. In some cases, the vendor may need
the chemical family name for biodiesel (the methyl esters of fats
and oils) to look up the informa-tion or even the exact chemical
name of some of the biodiesel components such as methyl oleate,
methyl linoleate, methyl palmitate, or methyl stearate. Oxi-dized
biodiesel and biodiesel blends can contain organic acids and other
compounds that can significantly accel-erate elastomer degradation.
(Published data on B100 material compatibility are summarized in
Appendix C.) There have not been significant material compatibility
issues with B20 unless the B20 has been oxidized.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
18
-
diesel as a blendstock, not as a neat fuel. If you want to use
B100 as a fuel, these recommendations should help:
• Contact other users of higher-level blends and B100.The
National Biodiesel Board (NBB) has namesof individuals and
businesses as well as refer-ence materials about storage, handling,
and useof higher-level blends and B100. If you manage afleet,
contact your Fleet Management Associationor Clean Cities Coalition
to find out if anyone nearyou has experience with B100 or blends
above B20.Ask your B100 supplier for recommendations.
• Ask other users what they did, how they did it,how long it
took, how much it cost, what problemsthey encountered, how long
they have been usinghigher-level blends or B100, and what kinds
ofengines and equipment use higher-level blends andB100 at their
sites.
• Discuss your needs with your vehicle manufacturerand ask for
advice, including any recommendationsfrom other U.S. fleet
customers.
• Replace materials you know will be problematicand institute a
monitoring program based on theinformation presented in section
3.6.4, MaterialsCompatibility.
• Plan and budget for the time and expense ofincreased fuel
filter changes or cleaning your fuelsystem when first starting to
use higher-level blendsand B100.
- Frozen after several days in cold weather in rail-cars
equipped with external steam coils (the fuel in the tank cars is
melted at the final destination with steam).
- In a blend with winter diesel, kerosene, or other low cloud
point fuel in either railcars or trucks.
Regardless of how the biodiesel arrives, procedures that prevent
the temperature of B100 from dropping below its cloud point must be
in place. The cloud point of the biodiesel, the biodiesel and
ambient temperatures, and the time the fuel is in transport should
all be considered when transporting B100 to ensure the fuel does
not freeze or can be reliquified.
Use of B100 and High Blend Levels
Most biodiesel currently in use involves blends of B20 or lower
in a variety of applications. The price and lack of regulatory
incentives have limited the experience with blend levels of B50 and
higher, although some niche markets are using higher blends.
High-level biodiesel blends are successfully used in underground
mining equipment. The ability of biodiesel to reduce PM emis-sions
and reduce human exposure to this criteria pol-lutant has driven
the industry to adopt higher blends of biodiesel. Thus, most of the
information in this section is intended for biodiesel use as a
blending component. In particular, Specification D6751 is for the
use of bio-
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
19
-
This section focuses on blending B100 with petroleum diesel to
make B6 to B20 blends, but the approach is similar for other blend
levels such as B2 or B5. As dis-cussed in the previous sections,
the performance prop-erties of B100 can be significantly different
from those of conventional diesel. Blending biodiesel into
petro-leum diesel can minimize these property differences and
retain some of the benefits of B100. B20 is popular because it
represents a good balance of cost, emissions, cold weather
performance, materials compatibility, and ability to act as a
solvent. B20 is also the minimum blend level that can be used for
EPAct compliance for covered fleets.
Specifications
B5 and Lower Blends
The specification for conventional diesel fuel, ASTM D975,
allows for up to 5 vol% biodiesel to be blended into compliant
diesel fuels. The biodiesel used in the blend must meet D6751.
Blends up to B5 must meet all the numeric requirements for diesel
fuel proper-ties specified in D975; none were changed or relaxed to
accommodate biodiesel. ASTM Method D7371, Stan-dard Test Method for
Determination of Biodiesel (Fatty Acid Methyl Esters) Content in
Diesel Fuel Oil Using Mid Infrared Spectroscopy (FTIR-ATR-PLS
Method), may be used to determine the biodiesel blend percent-age.
There is no requirement that D975-compliant fuels list the percent
of biodiesel in the blend. Users may not know if the fuel they are
using or purchasing is B0, B2, or B5 unless they measure the
biodiesel content using ASTM D7371 or an alternate method.
B6 to B20 Blends
The specification for B6 to B20 blends requires that the
biodiesel meet the D6751 specification prior to blend-
ing with diesel fuel. The general requirements of the B6-B20
specification, D7467-15cε1, are shown in Table 5. Beyond the
properties in Table 5, there are many other requirements within the
specification that are important for users. Consult the full
specification for additional details (available at astm.org). The
requirements are based on those in D975 with some additional
require-ments to ensure the fuel is fit-for-purpose. The 90%
distillation temperature is allowed to be 5°C higher than for D975
diesel fuel. The specification is designed such that if a
D6751-compliant B100 and a D975-compliant diesel fuel are blended,
the resultant blend will meet the specification. However, diesel
fuel that does not fully meet D975 can also be used (for example by
having inadequate lubricity, high sulfur, or high aromatics), and
biodiesel can be used to blend these properties into
compliance.
Pump Labeling
As part of the Energy Independence Security Act, the Federal
Trade Commission was required to publish bio-diesel pump labeling
requirements. Pumps are required to be labeled to inform consumers
about the percentage biodiesel being offered for sale. The rules
also cover renewable diesel (also called biomass-based diesel.18
Pumps selling up to B5 blends require no separate label-ing. Figure
5 shows the label for blends between B6 and B20. Although the label
indicates the blend is “B-20,” the regulations allow this label to
be used for any blend inclusively between B6 and B20. Blends higher
than B20 are required to be labeled with the exact blend
percent-age; for example, a B30 blend will have a pump label
stating the blend is B30.
It should be noted that these federal requirements are the
minimum necessary at pumps to inform consumers about the blends
they are purchasing. Individual states may have requirements that
exceed the federal requirements.
Biodiesel Blends
Figure 5. FTC-compliant B20 and B100 pump labels
B-100 Biodiesel
contains 100 percent biodiesel
B-20 BiodieselBlend
contains biomass-based diesel or biodiesel in quantities between
5 percent and
20 percent
18. Federal Register / Vol. 73, No. 48 / Tuesday, March 11, 2008
/ Proposed Rules. “Federal Trade Commission, 16 CFR Part 306 RIN
#3084–AA45, Automotive Fuel Ratings, Certification and Posting.”
ftc.gov/sites/default/files/documents/federal_register_notices/automotive-fuel-rating-certification-and-posting-16-cfr-part-306/
080311automotivefuelratings.pdf.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
20
http://www.astm.orghttps://www.ftc.gov/sites/default/files/documents/federal_register_notices/automotive-fuel-rating-certification-and-posting-16-cfr-part-306/080311automotivefuelratings.pdfhttps://www.ftc.gov/sites/default/files/documents/federal_register_notices/automotive-fuel-rating-certification-and-posting-16-cfr-part-306/080311automotivefuelratings.pdfhttps://www.ftc.gov/sites/default/files/documents/federal_register_notices/automotive-fuel-rating-certification-and-posting-16-cfr-part-306/080311automotivefuelratings.pdf
-
Table 5. ASTM D7467-15cε1 Specification for Diesel Blends B6 to
B20
PropertyTest
Method
Grade
B6 to B20 S15 B6 to B20 S500 B6 to B20 S5000
Acid Number, mg KOH/g, max. D664 0.3 0.3 0.3
Viscosity, mm2/s at 40°C D445 1.9 – 4.1a 1.9 – 4.1a 1.9 –
4.1a
Flash Point, °C, min D93 52b 52b 52b
Cloud Point, °C, max or LTFT/CFPP, °C, max
D2500 c c c
Sulfur Content, (μg/g or ppm) mass %, max. mass %, max.
D5453 D2622 D129
15 – –
– 0.05
–
– –
0.50
Distillation Temperature, °C, 90% evaporated, max.
D86 343 343 343
Ramsbottom carbon residue on 10% bottoms, mass %, max.
D524 0.35 0.35 0.35
Cetane Number, min. D613 40 40 40
One of the following must be met:(1) Cetane index, min.(2)
Aromaticity, vol%, max.
D976-80 D1319-03
40 35
40 35
40 –
Ash Content, mass %, max. D482 0.01 0.01 0.01
Water and Sediment, vol%, max. D2709 0.05 0.05 0.05
Copper Corrosion, 3 h @ 50°C, max. D130 No. 3 No. 3 No. 3
Biodiesel Content, % (V/V) D7371 6.– 20. 6.– 20. 6.– 20.
Oxidation Stability, hours, min. EN15751 6 6 6
Lubricity, HFRR @ 60°C, (micron), max. D6079 520 520 520
Note: Reprinted with permission of ASTM.
CFPP: cold filter plug point
LTFT: low-temperature flow test
a. If Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D
diesel fuel are used, the minimum viscosity shall be 1.3 mm2/s.
b. If Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D
diesel fuel are used or a cloud point of less than -12°C is
specified, theminimum flash point shall be 38°C.
c. It is unrealistic to specify low-temperature properties that
will ensure satisfactory operation at all ambient conditions.
However, satisfac-tory operation below the cloud point (or wax
appearance point) may be achieved depending on equipment design,
operating conditions,and the use of flow-improver additives as
described in Appendix X3.1.2 to the test method. Appropriate
low-temperature operabilityproperties should be agreed upon between
the fuel supplier and purchaser for the intended use and expected
ambient temperatures. TestMethods D4539 and D6371 may be useful to
estimate vehicle low-temperature operability limits when flow
improvers are used, but theiruse with Bxx blends from a full range
of biodiesel feedstock sources has not been validated. Due to fuel
delivery system, engine design,and test method differences,
low-temperature operability tests may not provide the same degree
of protection in various vehicle operat-ing classes. Tenth
percentile minimum air temperatures for U.S. locations are provided
in Appendix X3 as a means of estimating expectedregional
temperatures. The tenth percentile minimum air temperatures may be
used to estimate expected regional target temperatures foruse with
Test Methods D2500, D4539, and D6371. Refer to Appendix X3.1.3 for
further general guidance on test application.
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
21
-
Low-Temperature Properties
Blending biodiesel with petroleum diesel moderates
low-temperature operability problems of B100 by dilu-tion, although
the effects are not necessarily linear. Conventional
low-temperature operability additives can be used with blends as
these are believed to be effective in the petroleum portion of the
blend. When biodiesel is blended with diesel fuel, the key
variables are the cold flow properties of the diesel fuel, the
properties of the biodiesel, the blend level, and the effectiveness
of cold flow additives.
There are some critical metrics for low-temperature operability.
Note that cold filter plugging point (CFPP) and low-temperature
flow test (LTFT) are particu-larly useful for revealing the
presence of additives. For blends, these include:
• Cloud point. The temperature at which small solidcrystals are
first visually observed as the fuel iscooled (ASTM D2500, D5771,
D5772, or D5773).Below the cloud point of the blend, these
crystalsmight plug filters and/or drop to the bottom of avehicle or
storage tank. Cloud point is the mostwidely used and most
conservative estimate of thelow-temperature operability limit.
However, fuelscan usually be pumped at temperatures below thecloud
point.
• Pour point. The temperature at which the fuel con-tains so
many agglomerated crystals it is essentiallya gel and will no
longer flow (ASTM D97, D5949, orD5950). Distributors and blenders
use pour pointas an indicator of whether the fuel can be
pumped,even if it would not be suitable for use withoutheating or
taking other steps.
• Cold filter plugging point. This is the temperatureunder a
standard set of test conditions, as defined inASTM D6371, where a
fuel filter plugs. The CFPPtest employs rapid cooling conditions.
CFPP resultsmore than 10°C (18°F) below the cloud point shouldbe
viewed cautiously as they may not reflect the truelow-temperature
operability limit. The test simulatesthe performance of an average
or typical vehicleand is not protective of the most severe fuel
systemdesigns, which make up roughly one-third of heavy-duty
vehicles or one-fifth of light-duty vehicles.
• Low-temperature flow test. This test also reportsa temperature
under a standard set of conditions,defined in ASTM D4539, where a
fuel filter plugs.LTFT employs slow cooling at 1°C per hour
andsimulates the most severe (and common) fuel systemdesigns in
North American heavy-duty trucks fromthe standpoint of
low-temperature operability.
It is strongly recommended that you consult Appendix X.5 to ASTM
D975 or Appendix X.3 to ASTM D7467to understand the history and
relative utility of tests forcloud point, CFPP, and LTFT.
B100 cold flow properties depend on FAME composi-tion, which
affects the cold flow properties of blends (Figure 6 and Figure 7).
Measurements of cloud point and pour point are not exact, but have
±2°C (±3.5°F) repeatability. The same is true of diesel fuel. In
addi-tion, different No. 2 diesel fuels may have cloud points of
-35°C to -5°C (-31°F to 23°F). Some fuels can have
20
10
0
0
-10
-30
-20
0 20 40 60
Biodiesel Concentration, vol%
Pour
Poi
nt, °
C 20
10
-10
-30
-20
Clou
d Po
int,
°C
80 100
0 20 40 60
Biodiesel Concentration, vol%80 100
2C CP B100-3C CP B1014C CP B10020C CP B10023C CP B1008C CP
B100
2C CP B100-3C CP B1014C CP B10020C CP B10023C CP B1008C CP
B100
Figure 7 (bottom). Biodiesel/diesel blend pour point test
results
Figure 6 (top). Biodiesel/diesel blend cloud point test
results
Fundamentals of Biodiesel Ezekiel Enterprises, LLC
22
-
Deg
rees
C
YG 1 YG 2 Veg 1 Veg 2
B100
B20 w 80/20 (80/20 is an 80% blend of No. 2 diesel with No. 1
diesel [or kerosene])
B20 w D2
B20 w 60/40 (60/40 is a 60% blend of No. 2 diesel with 40% No. 1
diesel.)
-15
-10
-5
0
5
Cloud point of No. 2 is –11°C.Cloud point of No. 1 is –47°C.
cloud points higher or lower than these figures. No. 1 diesel,
jet A, or kerosene may have cloud points of -40°C to -51°C (-40°F
to -60°F). A recent CoordinatingResearch Council study showed that
biodiesel blends(B5 and B20), made from B100 meeting
D6751-08a,would provide operability down to cloud point. Addi-tives
may allow operation at even lower temperatures.19
From this same study, it was found that for biodiesel blends
prepared from B100 meeting D6751-08a, the cloud point and LTFT will
be nearly the same, and CFPP will be 2°C to 3°C (3.5°F to 5°F)
lower, if no low-temperature flow improver additives are used.
Addi-tives do not usually alter cloud point, but can lower CFPP and
LTFT. Thus, for additized fuels, CFPP or LTFT may be a better
predictor of low-temperature operability.
Blends of No. 1 and No. 2 diesel fuel are frequently used to
meet customer cold flow requirements (see Figure 8). Adjusting the
blend of kerosene (or No. 1 diesel) in the diesel fuel alone or
with additives can modify the cloud and pour point temperatures of
B20. An accurate esti-mate of how B20 will perform in the winter
months will require mixing the biodiesel with the winter diesel
typi-cally delivered in your area a